The brook stickleback (''Culaea inconstans'') is a small freshwater

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

that is distributed across the US and

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

. It grows to a length of about 2 inches. It occupies the northern part of the eastern United States, as well as the southern half of Canada. Small populations are scattered throughout the Mississippi-Great Lakes basin extending to

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

, New Mexico, Kentucky, Tennessee, etc., though some of these areas are not native to the species. This small fish inhabits clear, cool streams and lakes. They eat small

Invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

, insect larvae, and occasionally their own eggs. They are also preyed upon by

smallmouth bass The smallmouth bass (''Micropterus dolomieu'') is a species of freshwater fish in the Centrarchidae, sunfish family (biology), family (Centrarchidae) of the order (biology), order Centrarchiformes. It is the type species of its genus ''Micropterus ...

and

northern pike The northern pike (''Esox lucius'') is a species of carnivorous fish of the genus ''Esox'' (pikes). They are commonly found in brackish water, moderately salty and fresh waters of the Northern Hemisphere (''i.e.'' holarctic in distribution). T ...

. Feeding time is usually dawn and sunset. The brook stickleback does have active competition mostly from

minnow Minnow is the common name for a number of species of small freshwater fish, belonging to several genus, genera of the family Cyprinidae and in particular the subfamily Leuciscinae. They are also known in Ireland as wikt:pinkeen, pinkeens. While ...

s, but feeding times are different, along with diet.Stewart, D.B. 2007.''
Fish diets and food webs in the Northwest Territories: brook stickleback (''Culaea inconstans'').
Canadian Manuscript Report of Fisheries and Aquatic Sciences 2798: 1-17 Spawning occurs in midsummer. Males secure a territory, build a nest, and mate with females. Males provide protection for the

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

, ward off predators, and usually die later in the season. The nests are built out of aquatic grasses.Acere, T.O. 1986. Age, growth and life history of ''Culaea inconstans'' (Pisces: Gasterostidae) in Delta Marsh Lake Manitoba. Hydrobiologia 135: 35–44 This is considered an annual species. Though the brook stickleback is not considered a threatened species, deforesting and changing waters are altering ecosystems of the species. Harvesting of trees around riparian environments is having a large effect of the stream ecosystem where the brook stickleback resides.Chizinski, C. J. 2010. The influence of partial timber harvesting in riparian buffers on macroinvertebrate and fish communities in small streams in Minnesota, USA. Forest Ecology and Management 259: 1946-1958

Taxonomy

The brook stickleback was first formally described as ''Gasterosteus inconstans'' in 1840 by the American naturalist

Jared Potter Kirtland Jared Potter Kirtland (November 10, 1793 – December 10, 1877) was a naturalist, malacologist, and politician most active in the U.S. state of Ohio, where he served as a probate judge, and in the Ohio House of Representatives. He was also a phy ...

with its type locality given as

Trumbull County, Ohio Trumbull County is a County (United States), county in the far northeast portion of the U.S. state of Ohio. As of the 2020 United States census, 2020 census, the population was 201,977. Its county seat and largest city is Warren, Ohio, Warren, ...

. In 1876

David Starr Jordan David Starr Jordan (January 19, 1851 – September 19, 1931) was the founding president of Stanford University, serving from 1891 to 1913. He was an ichthyologist during his research career. Prior to serving as president of Stanford Universi ...

proposed the

monospecific genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

''Eucalia'' for the brook stickleback but Jordan's name was invalid because it was preoccupied in

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

. ''Culaea'' was then proposed as the replacement name in 1950 by

Gilbert Percy Whitley Gilbert Percy Whitley (9 June 1903 – 18 July 1975) was a British-born Australian ichthyologist and malacologist who was curator of fishes at the Australian Museum in Sydney for about 40 years. Early life and education Gilbert Percy Whitley ...

. The brook stickleback is the only species in the genus ''Culaea'' which is classified within the stickleback family, Gasterosteidae. ''Culea'' is a near anagram of ''Eucalia'' which is a combination of ''eu'', meaning "well" and ''calia'', meaning "nested", and allusion to the sticklebacks' building of nests. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''inconstans'' means "variable" and is a reference to the variable number of dorsal spines and fin rays in the dorsal and anal fins.

Description

The brook stickleback has a tapered body with a slim caudal peduncle and a fan-shaped tail. It very much resembles the

ninespine stickleback The ninespine stickleback (''Pungitius pungitius''), also called the ten-spined stickleback, is a freshwater species of fish in the family Gasterosteidae that inhabits temperate waters. It is widely but locally distributed throughout Eurasia and ...

(''Pungitius pungitius'') but only has five, or occasionally six, dorsal spines. It also lacks lateral bony plates. Most of the year the colouring is grayish or olive green with a varying amount of indistinct mottling, but during the spawning season, males are nearly black and females have darker and lighter patches. This species grows to a maximum length of .

Geographic distribution of species

''Culaea inconstans'' occurs throughout the southern half of Canada and the northern part of the eastern United States. It is one of the smallest fishes in the region. Brackish water populations are uncommon but certainly exist. It extends down to the southern reaches of the Mississippi River – Great Lakes drainage basins. Populations also exist in Colorado and Nebraska to the west, and in Alberta, Saskatchewan, Manitoba, and the Northwest Territories to the north. Though these are typically the native ranges of the brook stickleback, the species has been introduced to Alabama, Kentucky, Tennessee, northwestern Colorado, Wyoming, northeastern Utah and California, and even in parts of South Dakota and Washington State. Certain geographical distribution studies have found that certain populations may have been native in New Mexico and still exist today. Nebraska does have brook stickleback populations, but they are generally found in small streams in the northern portion of the state. The fish have been found in Nebraska since the early part of the nineteen hundreds. River drainages that sustain brook stickleback populations are the Loup, Middle Platt, Niobrara, and smaller distributions in the Lower Platte, Missouri River tributaries, North Platte, and South Platte. Though the species appears to have an abundant distribution across North America, the Nature Conservancy has declared the species to be a S3 (vulnerable) level. Reasons for the level of vulnerability could be due to increased dam construction, especially in the eastern United States. This can lead to a destruction of habitat, increase in silted waterways, alteration of stream nutrient transport, and damaged breeding grounds. Alteration of stream dynamics could also lead to a change in predator frequency, thus exposing the brook stickleback to unforeseen predators.

Introduction in Europe

The brook stickleback was introduced in upper drainage of the River Inn in Bavaria. And in the 1960s was accidentally introduced alongside ''

Micropterus ''Micropterus'' is a genus of North American freshwater fish collectively known as the black bass, which belong to the sunfish family (biology), family Centrarchidae of order (biology), order Centrarchiformes. They are sometimes erroneously cal ...

'' species to Lake Lohjanjarvi in southern

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

, where it has become established.

Ecology

As with a large geographical distribution, this species also lives in a wide range of flowing water habitats. Waterways such as rivers, streams, floodwater streams and drainages, lakes, ponds, potholes, hot springs, sinkholes, and seasonal melt water or spring fed ponds are all viable brook stickleback territories. Though the species can thrive in these habitats, primary spawning, breeding, and rearing grounds are located in shallow (< 1.5m) near shore environments with high vegetation cover and low velocity water. The species has a wide elevation range with specimens identified from sea level to ~ 2,400m.

Diet

The brook stickleback is an omnivore, with primary feeding tendencies toward aquatic insect larvae, adult terrestrial insects, crustaceans, fish eggs and larvae, snails, oligochaetes, nematodes, rotifers, and mites. However, brook stickleback feed on vascular plant material, as well as algae. Newly hatched stickleback larvae and planktonic crustaceans from both streams and ponds. Juveniles eat small organisms due to mouth size restrictions, and adults eat both large and small organisms.

Predators

Certain large

invertebrates Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...

birds Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...

, and

all prey on the brook stickleback. With its small size, this species of stickleback has evolved piercing spines and protective plates to hinder predators. With this protection, as well as advanced anti-predator behavior, the brook stickleback is only a minor prey item. In a lab study, adult water bugs (''

Lethocerus americanus ''Lethocerus americanus'', sometimes called the electric light bug, toe biter or fish killer, is a giant water bug in the family Belostomatidae, native to southern Canada and the United States (north of 35°N; other ''Lethocerus'' species are fo ...

'') and dragonfly nymphs ('' Aeschna'' spp.) both successfully preyed on the stickleback, but only in a night setting. Fish have been observed to be the most successful predator of the brook stickleback. Examples of these fish predators include yellow perch (''

Perca flavescens The yellow perch (''Perca flavescens''), commonly referred to as perch, striped perch, American perch or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Samuel Latham Mitchill fro ...

''), rock bass (''

Ambloplites rupestris The rock bass (''Ambloplites rupestris''), also known as the rock perch, goggle-eye, red eye, and black perch, is a freshwater fish native to east-central North America. This red-eyed fish is a species of freshwater fish in the sunfish family (Ce ...

''), creek chub (''

Semotilus atromaculatus ''Semotilus atromaculatus'', the creek chub or the common creek chub, is a species of freshwater ray-finned fish belonging to the family Leuciscidae. This species is found in the eastern US and Canada. Differing in size and color depending on or ...

''), burbot ('' Lota lota''), central mudminnow (''

Umbra limi The central mudminnow (''Umbra limi'') is a small fish in the family Umbridae of the order Esociformes. It is found in central and eastern North America in productive waters. It is fairly tolerant of low oxygen concentration In chemistry, conce ...

''), smallmouth bass (''

Micropterus dolomieu The smallmouth bass (''Micropterus dolomieu'') is a species of freshwater fish in the sunfish family (Centrarchidae) of the order Centrarchiformes. It is the type species of its genus ''Micropterus'' (black basses), and is a popular game fish sou ...

''), largemouth bass (''

Micropterus salmoides The largemouth bass (''Micropterus nigricans'') is a carnivorous, freshwater, ray-finned fish in the Centrarchidae (sunfish) family, native to the eastern and central United States, southeastern Canada and northern Mexico. It is known by a v ...

''), northern pike (''

Esox lucius The northern pike (''Esox lucius'') is a species of carnivorous fish of the genus ''Esox'' (pikes). They are commonly found in brackish water, moderately salty and fresh waters of the Northern Hemisphere (''i.e.'' holarctic in distribution). T ...

''), brook trout (''

Salvelinus fontinalis The brook trout (''Salvelinus fontinalis'') is a species of freshwater fish in the char genus ''Salvelinus'' of the salmon family Salmonidae native to Eastern North America in the United States and Canada. Two ecological forms of brook trout ha ...

''), rainbow trout (''

Oncorhynchus mykiss The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an anadromous (sea-run) form of the coastal ...

'') and round goby ('' Neogobius melanostomus''). Brook stickleback eggs can be cannibalized, as well as consumed by rainbow trout (''O. mykiss''). Competition among the ninespine stickleback exists. However, ninespine stickleback habitat exists in the pelagic zone, while the brook stickleback occupies the littoral zone. In the presence of fathead minnows (''

Pimephales promelas Fathead minnow (''Pimephales promelas''), also known as fathead or tuffy, is a species of freshwater ray-finned fish belonging to the family Leuciscidae, the shiners, daces and minnows. The natural geographic range extends throughout much of Nor ...

''), the brook stickleback has a more diverse diet since the fathead is a more generalist feeder.

Life history

For this particular species, spawning occurs in mid-summer. Brook sticklebacks migrate annually up affluent streams and creeks of rivers and lakes during the spring to spawn in weedy areas. Spawning occurs as males secure a protected territory and construct a nest. These nests are constructed using algae, roots, and aquatic vegetation. There is one entrance with no exit. When the female enters, she deposits her eggs by shaking violently. Each shake allows more eggs to be deposited. Once all the eggs have been placed, the female must push her way through the wall of the nest to exit. During this process, studies have shown that the female makes acoustic noises, which is thought to advertise to sneaker males, as this can increase the proportion of eggs fertilized.Kilgour, R. J., et al. 2010. The role of acoustic cues in the breeding repertoire of the brook stickleback. Journal of Ethology 28: 175–178. After spawning, the male assumes protection of the eggs which hatch in 7–11 days.Moodie, G. 1986. The Populations of ''Culaea inconstans'', The Brook Stickleback, in a small prairie lake. Canadian Journal of Zoology 64: 1709–1717. New hatched stickleback can wander from the nest, but the male gathers them into his mouth to deposit them back in the protective nest. Spawning usually ends around mid-July due to swift temperature changes in the water. The newly fertilized eggs are vulnerable to slight temperature changes. These fish grow rapidly during their first summer and typically reach sexual maturity by spring of the next year. Most adults die within the spawning season or shortly after causing them to be deemed an annual species.

Conservation

Although the Nature Conservancy has listed the brook stickleback as level S3 (vulnerable), the numbers of this species aren't threatened. The species is observed to be migrating westward and is seen as an invasive species in Wyoming. The strength of this species' success in its natural environment is seen in the amount of locations it has successfully colonized after the last ice age with the northern retreat of the glacial caps. However, there is a potential for the population of the brook stickleback to decrease. The spawning season for this species is relatively short with high sensitivity to temperature changes. Global temperature changes are at an unprecedented rise, which could eventually lead to a global shift in water temperature. This could highly affect the spawning season for the brook stickleback species. Protecting the habitats is key to preserving the integrity of local ecosystems, as well as the integrity of the species. It is found that stable habitats allow brook stickleback to have a longer lifespan. The brook stickleback can be found from the northern parts of the Canadian interior all the way down to southern reaches of the United States. Protection of this species should be on high priority because this species has led scientist in significant breakthroughs in sympatric and allopathic speciation.McLennan, D.A. 2008. Conservation and variation in the agonistic repertoire of the brook stickleback, ''Culaea inconstans.'' Environmental Biology of Fishes 82: 377–384. Tracking their progress in increasing or declining numbers would help conservationists categorize specific threats for that region.

References

* {{Authority control Gasterosteidae Fauna of the Plains-Midwest (United States) Fish of North America Fish of the Great Lakes Taxa named by Jared Potter Kirtland Fish described in 1840 Freshwater fish of North America